He added a second round two-under-par 70 to his first day 63 for a halfway total of 11-under-par.
The 34-year-old is two shots in front of Thailand’s Kwanchai Tannin (68), Phachara Khongwatmai (67), and Settee Prakongvech (67).
Two strokes further back are Thailand’s Danthai Boonma (69) and Krittitee Sunthornnon (68) in the fourth stop on the 2015 ASEAN PGA Tour.
Thai star Prayad Marksaeng, the current leader of the ASEAN PGA Tour Order of Merit thanks to victory in the Singha Pattaya Open in March, shot a 71 and is five off the lead.
Murillo, who turned professional in 2006 and first surfaced in the region by making it through the 2014 Asian Tour Qualifying School, made birdies on 17 and 18 to make sure he stayed on top of the leaderboard.
He made nine birdies in the first round but there were no such fireworks today as he made one other birdie and one bogey.
Making a strong move was Phachara who nailed six birdies and dropped one shot.
Two years ago, Phachara made headlines around the world when as a 14-year-old amateur he became the youngest golfer ever to win a professional event when he went 13 under at the Hua Hin Open.
Phachara was born on May 3, 1999, nearly seven months younger than New Zealand’s Lydia Ko when she won her first professional title, the New South Wales Open in January 2012, also at 14.
Japan’s Ryo Ishikawa had held the record prior to Ko, winning at the old age of 15 years and 8 months in 2007.
Defending champion Gunn Charoenkul from Thailand, winner of last year’s ASEAN PGA Tour Order of Merit with three victories, carded a 69 and trails Murillo by seven.
Thailand’s Prom Meesawat is tied with Gunn after returning a 68.